Print sheet transfer device

ABSTRACT

A print sheet transfer device has upstream rollers, downstream rollers, and a pair of first and second guide plates movable between a guide position and a release position for a print sheet. When the guide plate is moved from the guide position to the release position, the upstream side of the print sheet held with the upstream rollers is fed in a transfer direction in accordance with the movement. When the downstream side of the print sheet is held with or thrusted against the downstream rollers, a sag is formed in the print sheet between the upstream rollers and the downstream rollers. It is possible to easily perform an operation to remove the print sheet.

TECHNICAL FIELD

The present invention relates to a print sheet transfer device used as a unit to transfer a print sheet in, e.g., an image forming apparatus, and more particularly, to a print sheet transfer device capable of, when inconvenience has occurred in transfer timing or when a print sheet has been jammed in a transfer route (so-called paper jam), removing the print sheet from the transfer route with a simple manipulation.

BACKGROUND OF ART

There is an increasing need from users for downsizing of various apparatuses such as an image forming apparatus having the print sheet transfer device. To meet the requirement, the apparatuses tend to have complicated and high-density packaged internal structure. For this purpose, the print sheet transfer path is often provided in a deep inner part of the apparatus, and surrounded by other devices and constituents. In this case, upon removal of a print sheet jammed in the print sheet transfer path, the space to insert an operator's hand is extremely limited. In many cases, the print sheet is charged with static electricity by contact charge with the transfer path and is attached to the transfer path. It is very difficult to remove the print sheet.

Generally, when paper jam occurs in the print sheet transfer path of the print sheet transfer device, it is necessary to remove all the print sheets staying in the transfer path. However, in the image forming apparatus which is provided with the print sheet transfer device, the interval between the print sheets transferred with the print sheet transfer device is narrowed in accordance with accelerated image forming speed. The number of print sheets existing in the print sheet transfer path during the operation of the device tends to be increased. Accordingly, when paper jam occurs, the removal of all the large number of print sheets in the print sheet transfer path is very troublesome.

Japanese Published Unexamined Patent Application No. Hei 11-198470 discloses an invention of a print sheet transfer device with a purpose of removal of a jammed print sheet with ease from the print sheet transfer path of the print sheet transfer device. According to this print sheet transfer device, as shown in FIGS. 2 and 3, a pair of paper conveying rollers 7 are provided on an inner side surface of a jam access cover 2 with which a part of a paper conveying passage 17 is opened to the outside. The paper conveying rollers 7 are provided in an inverting section 18 of the paper conveying passage 17 to invert the print sheet transfer direction in an intermediate portion. Further, the print sheet transfer roller 7 is configured with a pair of driving roller 3 and driven roller 4. The driving roller 3 is provided inside from the driven roller 4 in the print sheet transfer device.

In the conventional print sheet transfer device, when an operator peers into the device to check the position of a jammed print sheet, the operator inserts his/her hand in the device to pull out the jammed print sheet from the device. The operation is troublesome, and the hand becomes dirty with toner, which is unpleasant for the operator. However, according to this invention, it is possible to pull out jammed print sheet in the print sheet transfer path to the outside by only opening the opening type cover. This simplifies the operation to remove the jammed print sheet upon occurrence of paper jam. Further, it is possible to comfortably perform the operation without getting the operator's hand dirty.

SUMMARY OF INVENTION Technical Problem

According to the invention of the print sheet transfer device disclosed in Japanese Published Unexamined Patent Application No. Hei 11-198470, it is possible to comparatively easily remove a jammed print sheet in a portion where the jam access cover to open a part of the print sheet transfer path can be provided. However, as described above, when paper jam occurs in the print sheet transfer path, it is necessary to remove all the large number of print sheets staying in the print sheet transfer path. Accordingly, it is necessary to provide the jam access cover in correspondence with many positions of the print sheet transfer path. However, many image forming apparatuses having the print sheet transfer device have a structural problem that there is no room for the special structure to open a part of the print sheet transfer path along with the print sheet conveying roller to the outside. Accordingly, in the structure of Japanese Published Unexamined Patent Application No. Hei 11-198470, it is difficult to easily remove a jammed print sheet and all the print sheets existing in the print sheet transfer path upon occurrence of paper jam with a hand.

The present invention has been made in view of the conventional technique and its problem, and aims to enable, in a print sheet transfer device, removal of a print sheet jammed in the print sheet transfer path and other print sheets staying in the print sheet transfer path upon occurrence of paper jam, easily with a hand.

Solution to Problem

According to a first aspect of the present invention, there is provided a print sheet transfer device including: an upstream roller that conveys a print sheet; a downstream roller that conveys the print sheet; a guide plate, provided between the upstream roller and the downstream roller, that is movable between a guide position to guide the print sheet and a release position to release the print sheet; a first interlocking mechanism that rotates at least one of the upstream roller and the downstream roller in accordance with an operation to move the guide plate from the guide position to the release position, to form a sag in the print sheet between the upstream roller and the downstream roller, and when the print sheet is transferred, does not transmit rotation of the upstream roller and the downstream roller to the guide plate.

According to a second aspect of the present invention, in the print sheet transfer device in the first aspect, the first interlocking mechanism rotates the upstream roller in a print sheet transfer direction in accordance with the operation to move the guide plate from the guide position to the release position, so as to feed the print sheet in contact with the upstream roller in the transfer direction, to form the sag in the print sheet.

According to a third aspect of the present invention, in the print sheet transfer device in the first aspect, the first interlocking mechanism rotates the downstream roller in an opposite direction to a print sheet transfer direction in accordance with the operation to move the guide plate from the guide position to the release position, so as to feed the print sheet in contact with the downstream roller in the opposite direction to the transfer direction, to form the sag in the print sheet.

According to a fourth aspect of the present invention, the print sheet transfer device in the second or third aspect further includes a second interlocking mechanism that rotates the downstream roller or the upstream roller in an opposite direction to a rotational direction of the upstream roller or the downstream roller in accordance with a rotation of the upstream roller or the downstream roller interlocked with the operation to move the guide plate from the guide position to the release position, so as to form the sag in the print sheet, and when the print sheet is transferred, does not transmit the rotation of the upstream roller or the downstream roller to the downstream roller or the upstream roller.

Advantageous Effects of Invention

According to the print sheet transfer device in the first aspect of the present invention, when the guide plate is moved from the guide position to the release position, at least one of the upstream roller and the downstream roller is rotated in accordance with the movement. Then the print sheet between the upstream roller and the downstream roller is fed, and a sag is formed between the both rollers. Further, upon transfer of the print sheet, the rotation of the upstream roller and the downstream roller is not transmitted to the guide plate, and there is no trouble in print sheet transfer.

According to the print sheet transfer device in the second aspect of the present invention, when the guide plate is moved from the guide position to the release position, the upstream roller is rotated in the print sheet transfer direction in accordance with the movement. The print sheet in contact with the upstream roller is fed in the transfer direction, and a sag is formed between the upstream roller and the downstream roller which stands still.

According to the print sheet transfer device in the third aspect of the present invention, when the guide plate is moved from the guide position to the release position, the downstream roller is rotated in the direction opposite to the print sheet transfer direction in accordance with the movement. The print sheet in contact with the downstream roller is fed in the direction opposite to the transfer direction, and a sag is formed between the upstream roller which stands still and the downstream roller.

According to the print sheet transfer device in the fourth aspect of the present invention, when the guide plate is moved from the guide position to the release position, the upstream roller is rotated in the print sheet transfer direction in accordance with the movement. The downstream roller is rotated in the direction opposite to the rotation of the upstream roller in accordance with the rotation of the upstream roller. As a result, a sag is formed in the print sheet between the upstream roller and the downstream roller. Otherwise, when the guide plate is moved from the guide position to the release position, the downstream roller is rotated in the direction opposite to the print sheet transfer direction in accordance with the movement. The upstream roller is rotated in the print sheet transfer direction in accordance with the rotation of the downstream roller. As a result, a large sag is formed in the print sheet between the upstream roller and the downstream roller. In transfer of the print sheet, the rotation of the upstream roller is not transmitted to the downstream roller, and the rotation of the downstream roller is not transmitted to the upstream roller. There is no trouble in the print sheet transfer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram schematically showing a structure of an image forming apparatus according to a first embodiment of the present invention;

FIG. 2 is a perspective diagram of a print sheet transfer device according to the first embodiment, viewed from a diagonal upper position, showing a state where a guide plate is set in a print sheet guide position;

FIG. 3 is a perspective diagram of the print sheet transfer device according to the first embodiment, viewed from the diagonal upper position, showing a state where the guide plate is set in a print sheet release position;

FIG. 4 is a perspective diagram of the print sheet transfer device according to the first embodiment, viewed from a front side, showing a state where the guide plate is set in the print sheet guide position;

FIG. 5 is a perspective diagram of the print sheet transfer device according to a second embodiment of the present invention, viewed from a diagonal upper position in the device, showing a state where the guide plate is set in the print sheet guide position; and

FIG. 6 is a perspective diagram of the print sheet transfer device according to the second embodiment, viewed from the diagonal upper position in the device, showing a state where the guide plate is set in the print sheet release position.

DESCRIPTION OF EMBODIMENTS 1. First Embodiment (FIG. 1 to FIG. 4) (1) Entire Configuration of Image Forming Apparatus

The present embodiment relates to an image forming apparatus having a print sheet transfer device.

As shown in FIG. 1, a transfer path 3 to guide a print sheet P is set in a casing 2 of an image forming apparatus 1. The transfer path 3 has a closed loop-shaped circulation path 7 configured with a horizontal lower path 4 to perform image formation on the print sheet P as a recording medium, a horizontal upper path 5 to reverse the print sheet P in which image formation has been made on its front surface and return the print sheet P to the lower path 4, and two connection paths 6 connecting respective both ends of the lower path 4 and the upper path 5. The print sheet P is subjected to image formation in the middle of transfer in the circulation path 7 in a counterclockwise direction in the figure.

As shown in FIG. 1, a paper feeding section 8 to feed the print sheet P is connected to the upstream side of the lower path 4 in the transfer path 3. The paper feeding section 8 is configured to feed the top print sheet P, among the print sheets P stacked on a paper feed table, vertically movable with an unshown mechanism, into the lower path 4. Further, in the transfer path 3, a belt transfer mechanism 9 as a conveyance section is provided on the lower side of a central portion of the lower path 4. The belt transfer mechanism 9 has a belt 10 which has a large number of unshown holes and which is circulate-driven, and a suction part 11 which sucks air downward from the holes of the belt 10 moving on the upper side to suck the print sheet P to the upper surface of the belt 10. It is possible to transfer the print sheet P, in a state where it is sucked to the upper surface of the belt 10, along the lower path 4.

Rollers 20 for transfer, as a transfer section for the print sheet P, are provided at arbitrary intervals at both ends of the lower path 4, the upper path 5 and the two connection paths 6, corresponding to both sides of the belt transfer mechanism 9. The print sheet P is transferred along these respective paths 4, 5 and 6 (7). Note that the rollers 20 are provided along the circulation path 7 in this manner, and in addition, are provided at arbitrary intervals in a paper discharge path and a switchback path branched from the circulation path 7 as described later.

An image forming section 30 is provided above the belt transfer mechanism 9 on the lower path 4. The image forming section 30 is a device having four ink-jet devices to discharge K (black) ink, C (cyan) ink, M (magenta) ink and Y (yellow) ink arrayed along a transfer direction of the print sheet P. It is possible to form a desired color image by discharging color ink on the upper surface of the print sheet P fed with the belt transfer mechanism 9.

A paper discharge path 21 provided with the rollers 20 is branched toward a diagonal upward direction on the downstream side of the upper path 5 in the circulation path 7. The terminal end of the paper discharge path 21 is connected to a paper discharge table 22 provided in the casing 2. The end side (downstream side) of the paper discharge table 22 is raised in a slope shape. The print sheet P, where the image has been formed with the image forming section 30 on the upper surface is discharged, in a faced down state (the upper surface is faced down), onto the paper discharge table 22. Further, the print sheet, where images are formed on the both surfaces, is discharged, with its surface first subjected to the image formation faced up, onto the paper discharge table 22.

In the circulation path 7, a switchback path 25 is branched in the middle of one of the connection paths 6 connecting the downstream side of the upper path 5 and the upstream side of the lower path 4, and slightly on the downstream side from the branching point of the paper discharge path 21. The switchback path 25 has a dead-end structure. Although the details are unshown, the rollers 20 are provided in the middle of the path. In this structure, the print sheet P, already subjected to image formation and guided from the circulation path 7 to the switchback path 25, is reciprocated in the switchback path 25, then returned to the circulation path 7. Thus the printing sheet P in the circulation path 7 is reversed. Accordingly, in this structure, it is possible to perform printing on the both surfaces of one print sheet P by a series of operations. That is, an image is formed with the ink-jet device (image forming section) 30 on one surface of the print sheet P while the print sheet P is transferred along the lower path 4 in the circulation path 7. Then, the print sheet P is sent from the upper path 5 into the switchback path 25. The print sheet P is sent backward from the switchback path 25 into the circulation path 7. Thus the print sheet P is reversed. The print sheet is transferred again along the lower path 4 and is passed in the vicinity of the ink-jet device (image forming section) 30, and another image is formed on the other surface of the print sheet P.

As described above, in the image forming apparatus 1 according to the present embodiment, the print sheet P is fed from the paper feeding section 8 into the lower path 4 in the circulation path 7. When an image is formed with the ink-jet device (image forming section) 30 on the surface of the print sheet P and the print sheet P is discharged to the paper discharge table 22, it is possible to discharge the print sheet with the image forming surface is faced down. This is single-sided printing of forming an image on only one surface of the print sheet P. Further, it is possible to perform double-sided printing of forming images on both surfaces of the print sheet P. In this case, the print sheet P with one surface subjected to the image formation is not discharged to the paper discharge table 22 but the print sheet P is guided to the switchback path 25. The print sheet P is reversed by being reciprocated in the switchback path 25, and then returned to the circulation path 7. The print sheet P is transferred again along the circulation path 7, and an image is formed with the ink-jet device (image forming section) 30, on the rear surface of the print sheet P. It is possible to discharge the print sheet P, with the surface first subjected to the image formation faced up, onto the paper discharge table 22.

(2) Configuration for Jammed Paper Removal in Print Sheet Transfer Device

The image forming apparatus 1 has a configuration for removing the print sheet P, when it is jammed in the print sheet transfer device, from the transfer path 3. In the image forming apparatus 1 shown in FIG. 1, an opening 40 (indicated with a broken line) to access the inner mechanisms is formed in a side plate of the casing 2, i.e., a plate body on the front surface side or rear surface side of the casing 2 provided orthogonally to the drawing surface of the figure. The opening 40 is opened or closed with an unshown door. The opening 40 and the door are provided in plural positions corresponding to the transfer path 3 for access to the print sheet P in any position of the transfer path 3. In FIG. 1, as a representative example, the opening 40 and the door are provided in the vicinity of a part of the upper path 5 close to the paper discharge path 21.

FIGS. 2 and 3 are perspective diagrams showing the opening 40 (indicated with an alternate long and short dash line) and a part of the print sheet transfer device provided in the casing 2, viewed from the outside through the casing 2 from a diagonal upper position. Further, FIG. 4 is a perspective diagram showing a part of the print sheet transfer device viewed through the casing 2 from the front surface side. The opening 40 is not shown. Note that these figures do not show the door to open/close the opening 40.

The print sheet transfer device has, as a pair of guide plates forming the transfer path 3, an upper first guide plate 41 and a lower second guide plate 42 provided in parallel to each other at a predetermined interval. Note that in this embodiment, the first guide plate 41 is on the upper side and the second guide plate 42 is on the lower side. However, the reference numerals are assigned merely to show relative positional relation. For example, as the connection paths 6 connecting the lower path 4 and the upper path 5 are paths provided in a vertical direction, the pair of guide plates are provided as a right side first guide plate and a left side second guide plate, in parallel to each other at a predetermined interval.

Further, the guide plates are provided in parallel to each other at a predetermined interval as a pair. However, the guide plates are not necessarily provided as a pair. For example, in a curved path provided in the vertical direction as in the case of the connection paths 6 connecting the lower path 4 with the upper path 5, the print sheet P may be guide-transferred along a concave surface side of one guide plate.

This print sheet transfer device has plural rollers 20 for transfer provided along the first guide plate 41 and the second guide plate 42. The plural rollers 20 are configured as plural pairs of rollers to transfer the print sheet P held between the rollers. In FIGS. 1 to 3, among the plural pairs of rollers, two pairs of rollers are shown. For the sake of convenience, respective rollers 20 of the pairs of rollers 20 on the upstream side with respect to a print sheet transfer direction F are referred to as upstream rollers 20 a, while respective rollers 20 of the pairs of rollers 20 on the downstream side with respect to the print sheet transfer direction F are referred to as downstream rollers 20 b.

Note that in the present embodiment, the rollers 20 are provided in pairs. However, even when the rollers 20 are not in pairs, it is possible to transfer the print sheet P. For example, it is possible to transfer the print sheet P while holding the print sheet P between the surface of one guide plate and one roller 20.

One of two rollers 20 forming a pair is a driving roller, and the other one, a driven roller. The two rollers 20 making up a pair are in contact with each other in the position of a through hole 43 formed in one or both of the first guide plate 41 and the second guide plate 42. It is possible to transfer the print sheet P along a gap between the first guide plate 41 and the second guide plate 42 by driving one of the rollers while holding the print sheet P between the rollers.

As shown in FIGS. 2 and 3, in the first guide plate 41 on the upper side, an edge on the upstream side orthogonal to the print sheet transfer direction F is fixed to a fulcrum shaft 45 via an accouplement 44. The fulcrum shaft 45 is rotatable. The fulcrum shaft 45 is provided in an adjacent part on the upstream side from the rotary shaft 46 of the upper upstream rollers 20 a and is in parallel to the rotary shaft 46 of the upper upstream rollers 20 a. Further, the first guide plate 41 on the upper side is divided into a downstream first plate body 41 a and an upstream second plate body 41 b along a parting line parallel to the direction orthogonal to the print sheet transfer direction F. The first plate body 41 a and the second plate body 41 b are rotatably connected with a hinge 47. Accordingly, the upstream second plate body 41 b is connected to the fulcrum shaft 45. Further, a jam clear lever 48, projecting to the outside of the casing 2 from the opening 40 from which the door is opened, is attached to a side edge of the first plate body 41 a on the downstream side. In FIG. 2, when an operator holds the jam clear lever 48 with his/her fingers and raises it, then as shown in FIG. 3, the first guide plate 41 swings upward about the fulcrum shaft 45 while it is bent in an upward-convex shape at the hinge 47, then the entire first guide plate 41 is lifted up away from the second guide plate 42. With this operation, when the print sheet P exists between the first guide plate 41 and the second guide plate 42, it is exposed. Accordingly, the print sheet P is easily removed upon occurrence of paper jam.

As shown in FIG. 2, the position of the guide plate when the first guide plate 41 and the second guide plate 42, facing each other at a predetermined interval, is referred to as a guide position to guide the print sheet P transferred with the rollers 20. Further, the position to lift up the first guide plate 41 by using the jam clear lever 48 to release the print sheet P in the gap between the first guide plate 41 and the second guide plate 42 is referred to as a release position to release the jammed print sheet P. It is possible to move the first guide plate 41 between the relatively lower guide position and the relatively upper release position within about a 90-degree range by manipulation of the jam clear lever 48. It is possible to selectively set the first guide plate 41 in the both positions.

Note that it may be configured such that the jam clear lever 48 is attached to the first plate body 41 a only when the door is opened to open the opening 40 and the jam clear lever 48 is used for jam clear. When the print sheet transfer device is used while the door is closed, the jam clear lever 48 is removed from the first plate body 41 a. Further, it may be configured such that the jam clear lever 48 is slidably attached to the first plate body 41 a along the direction orthogonal to the print sheet transfer direction F. When the print sheet transfer device is used while the door is closed, the jam clear lever 48 is inserted in the casing 2 and accommodated in a position not to interfere with the unshown door. Only when the door is opened to open the opening 40 and the jam clear lever 48 is used for jam clear, it is pulled out to the outside from the opening 40 of the casing 2.

As described above, the first guide plate 41 is rotatable about the fulcrum shaft 45. The present print sheet transfer device has a mechanism to rotate the upper side of the upstream rollers 20 a in a direction where the print sheet P is transferred in the print sheet transfer direction F in accordance with the rotation of the first guide plate 41, to feed the print sheet P between the upstream rollers 20 a and the downstream rollers 20 b, to form a sag as shown in FIG. 3. Hereinbelow, a first interlocking mechanism to form a sag in the print sheet P will be described.

Note that in the following description, as a simplified expression of “rotating the roller 20 in the direction where the print sheet P is transferred in the print sheet transfer direction F”, “rotating the roller 20 in the print sheet transfer direction F” will be used.

As shown in FIGS. 2 to 4, a first large gear 50 is connected to one end of the fulcrum shaft 45 connected to the first guide plate 41 on the opening 40 side. The first large gear 50 is engaged with a first small gear 51. The first small gear 51 is connected to the rotary shaft 46 coaxially with a second large gear 52. A second small gear 54 is attached via a one-way clutch 53 to the rotary shaft 46 of the upper roller 20 of the upstream rollers 20 a. The second large gear 52 is engaged with the second small gear 54.

The one-way clutch 53 between the rotary shaft 46 and the second small gear 54 of the upper upstream roller 20 a does not transmit rotation from the rotary shaft 46 to the second small gear 54, while transmitting rotation from the second small gear 54 to the rotary shaft 46. That is, when one of the upstream rollers 20 a is driven with a motor upon transfer of the print sheet P, the one-way clutch 53 does not transmit the rotation to the second small gear 54. When the second large gear 52 is rotated to drive the second small gear 54, the one-way clutch 53 transmits the rotational force to the rotary shaft 46 of the upper upstream roller 20 a.

According to the configuration for removal of jammed paper in the print sheet transfer device, the following operations are obtained regarding removal of print sheet P upon paper jam.

Assuming that paper jam occurs upon print sheet transfer and the print sheet P is to be removed from the transfer path 3, then the opening 40 of the casing 2 is opened, such that the jam clear lever 48 is projected to the outside of the opening 40, as shown in FIG. 2. The operator grasps the jam clear lever 48, and raises it in a direction opposite to the print sheet transfer direction F and upward.

As shown in FIG. 3, the first guide plate 41 swings upward about the fulcrum shaft 45 while it is bent with the hinge 47, lifted away from the second guide plate 42. With this operation, when the print sheet P exists between the first guide plate 41 and the second guide plate 42, it is exposed. Accordingly, upon occurrence of paper jam, the operator merely inserts his/her hand from the opening 40, and then easily removes the print sheet P.

As shown in FIG. 3, when the first guide plate 41 is moved from the guide position to the release position, the fulcrum shaft 45 is rotated in accordance with the movement, to rotate the first large gear 50 as indicated with an arrow. The rotation of the first large gear 50 rotates the second large gear 52 via the first small gear 51 as indicated with an arrow. The rotation of the second large gear 52 rotates the rotary shaft 46 of the upper upstream roller 20 a in the print sheet transfer direction F via the second small gear 54 and the one-way clutch 53. When the print sheet P is jammed between the upstream rollers 20 a and the downstream rollers 20 b, the print sheet P is fed to the downstream side, and stopped with the downstream rollers 20 b, thus a sag is formed between the both rollers 20 a and 20 b. The operator merely inserts his/her hand from the opening 40 to remove the print sheet P as described above. The print sheet P is automatically sagged in accordance with the operation to release the first guide plate 41 as described above. Accordingly, it is easier to remove the print sheet P.

In this manner, the formation of sag in the print sheet P in accordance with the operation of setting the first guide plate 41 in the release position, to facilitate removal of the print sheet P, is particularly advantageous when the upstream side of the print sheet P is held with the upstream rollers 20 a while the downstream side is free, or when the upstream side of the print sheet P is held with the upstream rollers 20 a while the downstream side is held with the downstream rollers 20 b. Other states than this state, i.e., when the print sheet P is held only with the downstream rollers 20 b, or when the print sheet P is not held with any of the upstream rollers 20 a and the downstream rollers 20 b, it is possible to easily take the print sheet P away with fingers, without sagging the print sheet P. Accordingly, in those states, it is not necessary to forcibly form a sag as in the case of the present embodiment.

Note that when the first guide plate 41 is a single plate body, the rotational radius of the first guide plate 41 about the fulcrum shaft 45 is the same as the length of the first guide plate 41 in the print sheet transfer direction F. The rotational radius of the jam clear lever 48 following the rotation of the first guide plate 41 is also the same as the length of the first guide plate 41 in the print sheet transfer direction F. Accordingly, a height H of the opening 40 should have a size to allow the rotation, i.e., the length of the first guide plate 41 in the print sheet transfer direction F. However, in the present embodiment, since the first guide plate 41 is configured with the first plate body 41 a and the second plate body 41 b connected with the hinge 47, it is bent between the first plate body 41 a and the second plate body 41 b upon rotation. Accordingly, the height H of the opening 40 is smaller than the length of the first guide plate 41 in the print sheet transfer direction F.

Upon print sheet transfer, the jam clear lever 48 is set to a state not to interfere with the unshown door from the state shown in FIG. 2 or 4, and the opening 40 of the casing 2 is closed with the door. The respective rollers 20 on the driving side of the print sheet transfer device are driven to transfer the print sheet P. When the respective driving side rollers 20 of the upstream rollers 20 a and downstream rollers 20 b are driven, the print sheet P is held between the upstream rollers 20 a the downstream rollers 20 b and transferred toward the downstream. At this time, the rotation of the upstream rollers 20 a is not transmitted via the respective gears to the fulcrum shaft 45. The fulcrum shaft 45 is not rotated to swing the first guide plate 41. That is, there is no trouble in the transfer of the print sheet P.

In the first embodiment, by setting the first guide plate 41 in the release position, the upstream rollers 20 a are rotated in the transfer direction. Then the print sheet P held with the upstream rollers 20 a is fed in the print sheet transfer direction F, to form a sag between the upstream rollers 20 a and the downstream rollers 20 b.

However, it is possible to adopt a mechanism to rotate the downstream rollers 20 b in an opposite direction to the transfer direction by setting the first guide plate 41 in the release position. The print sheet P held with the downstream rollers 20 b is fed in the direction opposite to the transfer direction, to form a sag between the downstream rollers 20 b and the upstream rollers 20 a. In this case, the direction to release the first guide plate 41 is opposite to that in the first embodiment. The downstream rollers 20 b are rotated in the opposite direction to the transfer direction in accordance with the operation to release the first guide plate 41.

Further, it is possible to adopt a mechanism to rotate the upstream rollers 20 a in the print sheet transfer direction F in accordance with the operation to release the first guide plate 41, and rotate the downstream rollers 20 b in the opposite direction to the print sheet transfer direction F. In this case, as long as the print sheet P between the upstream rollers 20 a and the downstream rollers 20 b is held with at least the upstream rollers 20 a or the downstream rollers 20 b, it is possible to form a sag in the print sheet P.

2. Second Embodiment (FIGS. 5 and 6)

The entire configuration of the image forming apparatus 1 in a second embodiment is the same as that in the first embodiment. The configuration of the print sheet transfer device different from that in the first embodiment will be described.

FIGS. 5 and 6 are perspective diagrams of a part of the print sheet transfer device provided in the casing 2, viewed through the casing 2 from a diagonal upper position, and viewed from the opposite side to that in FIG. 1 of the first embodiment. Note that in these figures, the opening 40 and the door to open/close the opening 40 exist in a deep inner part of the drawings, although they are not shown.

As shown in FIGS. 5 and 6, the print sheet transfer device has the first interlocking mechanism to interlock the first guide plate 41 with the upstream rollers 20 a as in the case of the first embodiment. Accordingly, when the first guide plate 41 is released, the upper side upstream rollers 20 a are rotated in the print sheet transfer direction F in accordance with the release operation of the first guide plate 41. The print sheet P held with the upstream rollers 20 a is fed in the print sheet transfer direction F. In addition, the print sheet transfer device has a second interlocking mechanism to interlock the upstream rollers 20 a with the downstream rollers 20 b. That is, the other end of the rotary shaft 46 of the upper upstream rollers 20 a and the other end of the rotary shaft 55 of the lower downstream rollers 20 b are connected with toothed belt pulleys 56. A toothed belt 57 is put around the two toothed belt pulleys 56. Further, a one-way clutch is provided at least between the other end of the rotary shaft 46 of the upper upstream rollers 20 a and the toothed belt pulley 56 or between the other end of the rotary shaft 55 of the lower downstream roller 20 b and the toothed belt pulley 56 (illustration is omitted).

With this one-way clutch, when the first guide plate 41 is set in the release position, the rotation of the rotary shaft 46 of the upper upstream rollers 20 a rotates the rotary shaft 55 of the lower downstream rollers 20 b in the opposite direction to the print sheet transfer direction F via the toothed belt pulley 56 and the toothed belt 57. When the upstream rollers 20 a and the downstream rollers 20 b are driven with the motor in the print sheet transfer direction F upon transfer of the print sheet P, the upstream rollers 20 a and the downstream rollers 20 b are not interlocked. The print sheet P is transferred without any trouble.

As shown in FIG. 6, in the print sheet transfer device, when the first guide plate 41 is moved from the guide position to the release position, the upper upstream rollers 20 a are rotated in the transfer direction of the print sheet P as indicated with an arrow in accordance with the movement of the first guide plate 41. Further, the rotation of the rotary shaft 46 holding the upstream rollers 20 a rotates the rotary shaft 55 of the lower downstream rollers 20 b in the opposite direction to the print sheet transfer direction F as indicated with an arrow via the two toothed belt pulleys 56 and the toothed belt 57. Accordingly, the upstream side end of the print sheet P held with the upstream rollers 20 a is fed in the print sheet transfer direction F, while the downstream side end of the print sheet P held with the downstream rollers 20 b is fed in the opposite direction to the print sheet transfer direction F. Accordingly, in comparison with the first embodiment, the print sheet P is further sagged between the upstream rollers 20 a and the downstream rollers 20 b. The print sheet P stopped by paper jam is more easily removed.

Note that as a modification to the second embodiment, the following configuration may be used. That is, the release direction of the first guide plate 41 is opposite to that in the second embodiment. The upper downstream rollers 20 b are rotated in the opposite direction to the transfer direction of the print sheet P in accordance with the movement of the first guide plate 41 to the release position. Further, the rotation of the rotary shaft holding the downstream rollers 20 b may rotate the rotary shaft of the lower upstream rollers 20 a in the print sheet transfer direction F via the two toothed belt pulleys 56 and the toothed belt 57. With this configuration, it is possible to form a sag larger than that in the first embodiment in the print sheet P as in the case of the second embodiment.

Further, in the print sheet transfer device according to the second embodiment, it is possible to infallibly form a sag in the print sheet P as long as the print sheet P is held with at least the upstream rollers 20 a or the downstream rollers 20 b.

Note that the print sheet transfer device described above in the respective embodiments is provided in the image forming apparatus 1. However, the purpose of the print sheet transfer device according to the embodiments is not limited to the image forming apparatus 1. It is applicable to all the apparatuses to transfer a sheet type material.

DESCRIPTION OF REFERENCE NUMERALS

Description of reference numerals given in the figures is as follows.

-   1 . . . image forming apparatus -   2 . . . casing -   3 . . . transfer path -   20 . . . roller for transfer -   20 a . . . upstream roller -   20 b . . . downstream roller -   41 . . . first guide plate -   41 a . . . first plate body -   41 b . . . second plate body -   42 . . . second guide plate -   45 . . . fulcrum shaft forming first interlocking mechanism -   46 . . . rotary shaft forming first interlocking mechanism -   50 . . . first large gear forming first interlocking mechanism -   51 . . . first small gear forming first interlocking mechanism -   52 . . . second large gear forming first interlocking mechanism -   53 . . . one-way clutch forming first interlocking mechanism -   54 . . . second small gear forming first interlocking mechanism -   56 . . . toothed belt pulley forming second interlocking mechanism -   57 . . . toothed belt forming second interlocking mechanism -   F . . . print sheet transfer direction -   P . . . print sheet 

1. A print sheet transfer device comprising: an upstream roller that conveys a print sheet; a downstream roller that conveys the print sheet; a guide plate, provided between the upstream roller and the downstream roller, that is movable between a guide position to guide the print sheet and a release position to release the print sheet; a first interlocking mechanism that rotates at least one of the upstream roller and the downstream roller in accordance with an operation to move the guide plate from the guide position to the release position, to form a sag in the print sheet between the upstream roller and the downstream roller, and when the print sheet is transferred, does not transmit rotation of the upstream roller and the downstream roller to the guide plate.
 2. The print sheet transfer device according to claim 1, wherein the first interlocking mechanism rotates the upstream roller in a print sheet transfer direction in accordance with the operation to move the guide plate from the guide position to the release position, so as to feed the print sheet in contact with the upstream roller in the transfer direction, to form the sag in the print sheet.
 3. The print sheet transfer device according to claim 1, wherein the first interlocking mechanism rotates the downstream roller in an opposite direction to a print sheet transfer direction in accordance with the operation to move the guide plate from the guide position to the release position, so as to feed the print sheet in contact with the downstream roller in the opposite direction to the transfer direction, to form the sag in the print sheet.
 4. The print sheet transfer device according to claim 2, further comprising a second interlocking mechanism that rotates the downstream roller or the upstream roller in an opposite direction to a rotational direction of the upstream roller or the downstream roller in accordance with a rotation of the upstream roller or the downstream roller interlocked with the operation to move the guide plate from the guide position to the release position, so as to form the sag in the print sheet, and when the print sheet is transferred, does not transmit the rotation of the upstream roller or the downstream roller to the downstream roller or the upstream roller. 